Names of two girls sharing mother in this part of France (8)
I believe the answer is:
normandy
This could be a double definition.
'names of two girls sharing mother in this part' is the first definition.
'normandy' can be an answer for 'part' (I have seen 'Part of France' mean 'normandy' so perhaps 'part' could also mean 'normandy'). I'm unsure of the rest of the definition.
'france' is the second definition.
(I've seen this before)
'of' acts as a link.
(Other definitions for normandy that I've seen before include "Area of Northern France" , "Region of northwest France" , "duchy" , "Province of northern France" , "Region of northern France" .)